Safety for the production process of high temperature return pouch

1. Balanced base metal thickness, good corona treatment effect, and high heat shrinkage rate

The commonly used high temperature retort bag substrate is pet, NY, AL, RCPP, etc. The corona treatment effect of this substrate directly affects the strength of high temperature retort bag composite; During the high temperature cooking process, the substrate reaches various degrees. The corona treatment of the material does not achieve the expected effect, the strength of the composite is low, and there is not enough strength between the layers of the composite bag to block the shrinkage of the substrate, resulting in a serious delay in the bag coating after high temperature cooking. In general, the surface tension of pets and NY used for high temperature retort pouches should reach 50mN / m, and RCPP should reach 40 ~ 42mN / m. In addition, certain additives in the substrate, such as anti-blocking agents, anti-slip agents, and antistatic agents, are released to the surface at an accelerated high temperature rate, which may lead to adhesive drop. Because the high temperature and high temperature retort bag is basically in the water during the sterilization process, when measuring the shrinkage matrix, the shrinkage of the matrix should be measured at 120 ° C for 30 minutes. The shrinkage rate should be small and stable, especially for BOPA film, RCPP film, SCPP film, and professional shrinkage rate and horizontal humidity Recommended not to be more than 1.5%, which can be called cooking grade film.

The balance thickness of each layer of the material should be uniform, the thickness deviation should not exceed 7%, and the physical and mechanical properties should meet the requirements.

With aluminum foil products, in addition to mechanical property parameters, the aluminum surface must be dry, A and B And Clean must meet the standards, that is, when inspecting distilled water, the product must be wet and the number of pores must be this small. Well, it cannot be stored for more than three months before use. In order to improve the resistance to compounds, BOPA of the intermediate compound must be a double-sided corona, and the corona value should be not less than 50 dynes.

2. Compatibility of cooking ink, glue and substrate

The production of composite packaging bags is the process of maintaining various properties of various materials, so it requires substrates, inks, glue, etc. It has good compatibility and high temperature, heat and moisture resistance. The degree of matching between them is very important. If the match is not good, the processed products may have appearance or delamination during the poor cooking process. According to bond theory, when the adhesive and adhering have the same surface tension and the same polarity, the tension between the faces is the lowest and the bond strength is the highest. As a result, the surface conditions of the ink and glue after curing into the film and the surface conditions of the substrate may vary depending on the manufacturer's product. Whether groups on different surfaces may be attracted to form intermolecular forces or chemical reactions to form chemical bonds. It determines whether various surfaces have good adhesives or not. Therefore, the types of ink and resin glue should be fully considered when making steaming bags, thus avoiding the poor overall performance of steaming bags due to incompatibility of ink, glue and substrate.

The ink or glue used for high temperature retort bags generally has a two-component polyurethane resin type. The heat resistance of the ink or glue depends on the heat and moisture resistance of the polyurethane resin. High temperature increases the re-activity characteristics of the ink adhesive. If the temperature and moisture resistance of the ink and glue are insufficient, hydroolysis will occur at high temperature, and the strength of the composite will be reduced. From the characteristics of the polyurethane resin system, the amino and ester groups in the resin have very strong polarity, and are prone to moisture erosion and hydrolysis in humid and hot conditions. The hydrogen bonding between the polyurethane resin and the substrate surface is easily damaged, reducing the bonding strength and even peeling off the bonding layer. At present, the inks and glues used in high-temperature retort bags are modified with resins or additives to improve the adhesion and heat resistance of inks and glues. Therefore, the quality of the modified resin used in the ink and determine the quality of the ink and adhesive. RCPP and SCPP of the heat sealing layer are selected according to different cooking temperatures.

RCPP or SCPP is usually used for heat sealing materials above 121 ° C, and the thickness should be greater than 60um. It is generally recommended to use imported products. The inner layer of imported RCPP contains rubber components, which are impact-resistant copolymer and polypropylene blocks.

3. Control healing time and glue amount

Due to the special sterilization method and the use conditions of high temperature retort bags, it is determined that high temperature retort bags need to have good composite strength to reduce the influence of damp heat conditions on the quality of high temperature retort bags, And the strength of the composite is related to the amount of glue and curing time. In general, the amount of high temperature retort bag gluing needs to reach more than 4g / m2; The healing time is another important factor affecting the strength of composites, the high temperature cooking bag healing time is generally more than 72 hours, although this time can not be achieved, The adhesive layer is also dry after peeling off, it seems to be complete, but in the process of high temperature treatment in fact, because there is still residual stress in it, it will still be far from the product with sufficient healing time in terms of heat and moisture resistance, And in the subsequent bag making process, it is easy to produce a thermal separation factor. Therefore, in the production process of high temperature and high temperature retort bags, we should not seek speed blindly, and should focus on the quality of high temperature retort bags and produce strictly according to the requirements of the process.

4. Gold, silver and ink should not be used as high temperature retort pouch

Gold and silver ink is very easy to penetrate pigment colors, such as red, light blue, purple ink when exposed to water, coupled with high temperature, it will inevitably dissolve. The copper powder and aluminum powder used in gold and silver ink are relatively active metals, which are easy to react chemically with moisture, fat and oxygen at high temperatures. After oxidation reaction, it looks blackish, green or even faded. Therefore, gold, silver ink, and penetrating ink cannot be used as high-temperature retor bag products.